This application represents a competing continuation of a project originally designed to assess whether calcium-channel blockers, given as anti-hypertensive therapy to patients with hypertension, increase the risk of myocardial infarction (MI). Based on the results of the secondary-prevention clinical trials, the study hypothesized an adverse effect. In the study, calcium-channel blockers were associated with a 57% increased risk of myocardial infarction in patients with high blood pressure (relative risk [RR] = 1.57, 95% confidence interval [CI] = 1.21 - 2.04). Pilot-study data also suggest an adverse effect of calcium-channel blockers on the outcome of stroke (RR = 2.56, 95% CI = 0.88-7.49). In this competing continuation, it is proposed to determine: 1) whether calcium-channel blockers increase the risk of stroke among hypertensive patients; and 2) whether individual calcium-channel blocking agents representing the three major subclasses increase the risks of MI and of the combined endpoint of MI and stroke in patients with high blood pressure. The setting is Group Health Cooperative (GHC). The investigators will use the GHC computerized files to identify all treated hypertensive patients, aged 30 to 79 yrs., with incident MI or stroke during July 1989-Dec 1998. Population-based controls with treated hypertension will be sampled from the GHC enrollment files. Data collection will include review of the ambulatory medical record and telephone interviews of consenting cases and controls (or proxies). The GHC computerized pharmacy records will serve as the primary source of information about the use of calcium-channel blockers. Frequency matching will control for the potential confounding effects of age, gender and year of presentation, and data analysis will involve restriction, stratification, and logistic regression. This study will have 80% power to detect a relative risk of 1.66 for the association between stroke and calcium- channel blockers. For individual calcium-channel blocking agents, the study will have 74-94% power to detect RRs in the range of 1.4-1.5 for MI and 72-91% power to detect RRs in the range of 1.3-1.4 for the combined endpoint of MI plus stroke.